I have been looking around for awhile but I'm not making sense of it. When I use the index I can't find the "applyGravity" code.
new113 wrote ...
2017/1/1
How do you apply gravity?
Applying gravity is just adding a constant value to the vertical speed of an actor:
Afterwards, collision with objects will be looked for. If 'vSpeed' is positive and an object is hit, then it came down on something and its position will need to be adjusted to place it above that object. If 'vSpeed' is negative and an object is hit, then it bopped it head on something and, again, positional adjustment may be necessary. The vertical speed should be set to zero if anything is hit regardless of the value of 'vSpeed'.
// with a class constant public static final int GRAVITY = 1; // gravity constant // and instance field private int vSpeed; // for current vertical speed // then, in act or method it calls vSpeed = vSpeed + GRAVITY; // apply gravity setLocation(getX(), getY()+vSpeed); // move vertically
Also what I want to do is keep the actor on a platform and if it comes off the gravity effect will happen. I have tried to use a code,
if (!getIntersectingObjects(platform.class).isEmpty())
{
move(0);
}
and its not been working (as you can tell I'm quite new to Greenfoot).
Is there any where could I find codes like the code given for gravity? Thank you for your help so far.
new113 wrote...
Also what I want to do is keep the actor on a platform and if it comes off the gravity effect will happen.danpost wrote...
Afterwards (after the movement code given), collision with objects will be looked for. If 'vSpeed' is positive and an object is hit, then it came down on something and its position will need to be adjusted to place it above that object. I have tried to use a code,
and its not been working (as you can tell I'm quite new to Greenfoot).
Yes. That is a newbee mistake. Telling something NOT to move does not accomplish anything as it will not move until some code has it move.
You want the actor to potentially move vertically every act cycle. When standing on something, it will move down one and then move back up one. The combined result will be that the actor will remain at the same vertical height for consecutive act cycles. The individual steps within the execution of the act method are not shown to the user -- only the end result. So, after applying gravity and falling (or rising, depending on the sign of 'vSpeed'), you would do something like this:
if (!getIntersectingObjects(platform.class).isEmpty())
{
move(0);
}int dir = (int)Math.signum(vSpeed); // 1, 0 or -1 (direction of vertical movement)
while(isTouching(platform.class))
{
setLocation(getX(), getY()-dir); // edging back off the platform
vSpeed = 0; // kill speed on hitting a platform
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